Conventionally, for example, in rolling of shaped steel, in order to upgrade the quality of rolled materials and to achieve labor-savings and energy-savings, mill rolls that can tolerate comparatively severe rolling conditions and have long lives have been in demand.
Due to this, for instance, as described in Patent Literature 1, mill rolls such as one in which a surface part of a roll barrel member is composed of hard metal (e.g., high-speed steel type multi-alloyed white cast iron) have been being used. This mill roll has been manufactured by removing a mill roll, in which a roll barrel member and shaft materials are integrated, from a material for rolls by scraping, the material for rolls being provided with a hard metal layer formed on an outer circumference of a core material, the shaft materials being singly provided on both sides in an axial direction of the roll barrel member.
However, when removing a mill roll having long shaft materials from a material for rolls by scraping, the amount of extra machining allowance at the time of removing by scraping increases, failing to shorten the manufacturing time. Also, running costs of cutting blades are incurred, which is uneconomical. Moreover, since it becomes impossible to manufacture a plurality of mill rolls from one material for rolls, for example, there is a need to prepare a new material for rolls, and it has been difficult to shorten the delivery time of and to reduce the manufacturing cost of mill rolls.
Therefore, for example, as with Patent Literature 2, there has been a proposal of a method for joining a roll barrel member and shaft materials by providing grooves singly to and arranging shaft materials singly on both sides of the roll barrel member and welding the respective grooves.